Exploration system based on WF-T-1 absolute gravimeter
（服务）：Exploration of Oil and Natural Gas、Ore and petroleum exploration,Seismic Applications
(Cases)Absolute gravimeter field gravity station fixed point measurement - Xinjiang 、Absolute gravimeter field gravity station fixed point measurement-Xi'an
WF-T-1 Absolute Gravimeter System Adjustment Manual
I. WF-T-1 High Precision Absolute Gravimeter Introduction
Model T-1 high precision absolute gravimeter is the first high precision absolute gravimeter independently developed and built by the Joint Laboratory of Precision Measurement of Tsinghua University.Model T-1 absolute gravimeter has carried out a large number of measurements for validation in the Joint Laboratory of Precision Measurement of Tsinghua University and Changping Campus of China Academy of Measurement Sciences, and also participated in the regional and international absolute gravity meter comparisons for a number of times and achieved better results. In addition, it has also traveled to Xi'an and Xinjiang to conduct field tests, all of which have yielded satisfactory measurement results.
The mechanical part of the gravimeter consists of three main parts, vacuum cavity, interferometer and vibration isolation. The vacuum cavity and vibration isolation are solidly connected together, and the vibration isolation adopts super spring. The vacuum cavity interferometer is directly installed on the ground through the adjustable three-legged bracket, and the vibration isolation seat is directly installed on the ground in the adjustable bracket.
| parameters | Indicators/requirements |
|---|---|
| range (of a measuring instrument) | ≥6000 × 10-5 ms–² |
| accurate | ≤10 × 10-8 ms–² |
| accuracy | ≤10 × 10-⁸ ms–² |
| power of resolution | ≤1 × 10-⁸ ms–² |
| Repeatability standard deviation | ≤10 × 10-8 ms–² |
| Resistant to magnetic field interference | <0.125 × 10-8ms–²/(A-m-¹) |
| Resistant to the effects of air pressure | <1 × 10-⁹ ms–² |
| connector | RS232C, USB, CANBUS, TCP/IP protocol interface, support for the “fifteen” communication and interface protocols |
| timing function | GNSS timing: manual |
| sampling rate | Not less than 0.1 Hz |
| Instrument operating temperature range | 20 °C ~ 30 °C |
| Instrument operating relative humidity range | ≤ 90% |
| electricity supply | Allowable range of steady state voltage: 220 × (1 ± 10%) V Allowable range of steady state frequency: 50 × (1 ± 5%) Hz |
| safety performance | electric shock protectionThe performance should be in line with the national standard GB 4706.1-2005, which stipulates the requirements of Class I appliances. Electrical Strength Voltage: The instrument should be able to withstand 1750 V (RMS) for 1 min between the AC voltage input and the case. leakage current: The secondary leakage from the instrument AC transformer to the enclosure is less than 3.5 mA peak. |
Areas of application already in place
1 Geophysics
- Earthquake prediction studies
- Solid Tide Monitoring
- Research on crustal movements
2 Gravity Criteria
- Gravity standard station
- Relative Gravity Grid Control Points
3 Resource exploration
- Oil and gas exploration
- Mineral exploration
On-site photos
考光，轻微震动干涉仪找到晃动的酒精反射光，通过调整支撑干涉仪腔体的3个立柱使酒精反射的测量光与参考光精确重合。
隔振启动
All operations in this step are limited to the vibration isolation and its accompanying controller and other accessories.
1. Turn on the power.
2. Open the mechanical lock (slowly rotate the downward locking arrow on top of the base to upward). This step has been done before and is only used here to check that it is on.
3. When the sphere waveform is stabilized, the leftmost auto will adjust the zero, and then turn it back to off gear.
4. Connect the photodetector signal to an oscilloscope for observation.
5. After the sphere waveform is stabilized, turn on the coil switch, at this time, you should be able to see the interference fringes on the oscilloscope changes in density, so that
The change is half a cycle (tens of seconds or more).
6. After the detector signal does not show a significant cycle (random wandering), connect it back to the acquisition card.
7. If vibration starts, adjust total gain R37 (decrease counterclockwise)
包络检查（检查真空腔垂直及测量光和参考光重合）
Motor motor repeated program, observe the oscilloscope waveform, check the interference waveform and peak-to-peak value, the falling and rising waveform should be the size of the peaks and peaks are stable and consistent.
If there is a change in the slope of the peak value of the interference waveform, it means that the path of the falling body movement and the interferometer output light is not good enough, at this time it is necessary to re-adjust the interferometer tilt angle, it is recommended to place a coordinate paper on top of the vibration isolation to observe the displacement of the light emitted from the upper cone prism (i.e., the measurement of the light), you can judge the direction of the tilt of the falling body trajectory according to the light displacement to determine how to tilt the interferometer until the naked eye can not be detected by the displacement of light, if the If the point of light is too bright to observe the point of light can be enlarged to observe, note that after the observation of the enlarged light spot outline and light spot inside the light and dark areas are unchanged and uniformly filled with bright spots.
If the peak-to-peak value is too small (less than 2 volts or so) it means that the measurement light and reference light coincidence is not good enough, you need to go back to the second step of the measurement light and reference light coincidence adjustment, usually does not appear this situation.
T1 Laser Interferometric Absolute Gravimetry Main Configuration List
| Serial Number | 部件（系统）名称 | 型号 | 性能指标 | 主要功能 | 数量 | 原产地和制造商 |
| 1 | 真空下落腔 | 自研 | 有效下落时长 | 实现真空下落 | 1 | 中国 |
| 2 | 超低频隔振 | 自研 | 本征周期30s | 隔绝环境低频振动干扰 | 1 | 中国 |
| 3 | 控制电脑 | 京特尔GM300 | R55600G+16G+500G | 运行控制程序 | 1 | 中国 |
| 4 | 激光器 | REO | 1.6mW 633nm | 提供激光 | 1 | 美国 |
| 5 | 控制柜 | 自制 | 支撑电气设备等 | 1 | 中国 | |
| 6 | 干涉仪 | 自制 | 激光干涉和探测 | 1 | 中国 |